Spatiotemporal Modeling of Soil Organic Carbon Stocks Across a Subtropical Region.

Given the significance and complex nature of soil organic carbon in the context of the global carbon cycle, the need exists for more accurate and economically feasible means of soil organic carbon assessment and its underlying spatial variation at regional scale. The overarching goal of this study was to assess both the spatial and temporal variability of soil organic carbon within a subtropical region of Florida, USA. Specifically, the objectives were to: i) quantify regional soil organic carbon stocks for historical and current conditions and ii) determine whether the soils have acted as a net sink or a net source for atmospheric carbon-dioxide over an approximate 40 year time period. To achieve these objectives, geostatistical interpolation models were used in conjunction with “historical” and “current” datasets to predict soil organic carbon stock for the upper 20 cm soil profile of the study area. Additionally, a paired resampling of historical sites was performed and supported findings from the geostatistical estimates. On average, soil organic carbon increased by 0.8 g m^-2 yr^-1 and 0.3 kg m^-2 yr^-1, according to the paired resampling and geostatistical techniques, respectively. These findings highlight the dynamic nature of soil organic carbon through space and time and indicate that the soils in this region have acted as a net sink for atmospheric carbon over the last 40 years. Accurately assessing the spatial and temporal state of soil organic carbon at regional scales is critical for improving global carbon stock assessments and to further our understanding of carbon dynamics by establishing a baseline so that relationships between soil carbon and abiotic and biotic components can be evaluated.